Agriculture Reference
In-Depth Information
nutrients added to the water they are growing
in, a highly artificial soil solution made up of
industrially produced fertilisers. This system
is highly efficient in terms of plant growth of
a particular species as the soil solution can be
tailored to the crop's needs. When we create a
diverse landscape, however, be it a food or
ornamental garden or a public open space,
the soil will determine the plant selection and
its relative success.
soil texture is to get a handful of it and
feel it. Knead the soil in your hands and
focus on how it feels. Sandy soils have large
particles that can be easily felt individually;
heavy clay soils have extremely small
particles so that it feels smooth and
sometimes silky, like plasticine. Most soils
will be somewhere in the middle. If you can
fashion the soil into a roll or ribbon that
holds together easily, you have clay soil. If
the soil holds together brief ly and you can
feel both gritty and smooth elements, it will
be loam. If it does not hold a shape it will be
sand (see Figure 1.10).
What is it?
Soil is made up of a few basic components
that vary in proportion with every soil.
Mineral particles of varying sizes that are the
result of rock weathering make up the bulk of
most soils. The predominant size of these
particles determines the texture of the soil
and also its nutrient-carrying capacity (see
below). Organic matter both living and dead
is a vital if all too small component of soil. It
can influence soil structure (see below), water
and nutrient-holding capacity as well as
providing habitat for all sorts of micro-
organisms. This organic life can range from
earthworms to soil fungi to viruses. The
remainder of the soil is taken up with water
and air.
Clay soil has a better water- and nutrient-
holding capacity compared to sandy soil;
however, it may have a poor drainage capacity
causing lack of air in the soil profile that can
lead to water logging. Sandy soil, on the other
hand, is perfectly drained (and more prone
to drought) as water flows through it easily.
Unfortunately, nutrients also find it difficult
to remain in sandy soil as they wash through
the gaps between the large particles.
These problems can be ameliorated with the
plentiful addition of well-rotted organic
matter, the addition of bentonite and zeolites
to sandy soils and gypsum to clay soils.
It is the balance of these four components
that determines its suitability for plant
growth. There is sure to be a suite of plants
that prefer the particular soil you have. Soils
are as varied as the plants they support.
Soil structure
Good soil structure is vital. It differs from soil
texture in that it is how the soil particles stick
together (or not) rather than the actual size
of the particles.
Soil texture
Soil texture is determined by the
predominant size of the mineral particles
that make it up. The best way to assess your
Well-structured soil should form aggregates
or crumbs of soil that are a mixture of
mineral and organic particles clumping
together (see Figure 1.10b).
